The Zoophytes. 305 
form colonies, nor do they deposit hard structures like 
their coral-forming relations. From the structural 
simplicity of these beings, it will be seen that a more 
inaccurate term than the popular one of coral-insetl, 
could hardly have been applied to these organisms ; and 
the term is moreover a senseless one, since, apart from 
the fact that the coral-polyps have no direct relationship 
whatever with the insects, there is not a vestige of 
resemblance between the two types, either in their 
external form or in their mode of life, to give in excuse 
for the application of the name. 
Throughout the group of the Zoophytes, the growth or 
increase in size of a colony takes place by the con- 
tinuous development of other individuals from the 
component polyps, either by their division into two, or by 
the production of buds around them ; but the increase in 
number of the colonies depends upon the production of 
true sexual elements, except in those special cases where, 
by mechanical means, a detachment of the buds or 
rupture of the branches takes place, in both of which 
cases fresh colonies develop from the detached pieces. 
In the little fresh-water polyp or Hydra, as already 
noticed, the buds produced normally separate from the 
parent form, but, in addition, true sexual elements are 
developed in the form of special buds, at certain times ; 
and in the closely related colonial forms, in which the 
individual feeding-polyps are essentially nothing but 
specimens of Hydra — and hence on this account known 
as the Hydroid Zoophytes — corresponding special buds 
are developed for the production of the sexual elements. 
One of the most striking instances of a marvellous 
series of phenomena, prevalent both among plants and 
